Well-established power distribution systems exist throughout most of the United States, and other countries, which provide power to customers via power lines. With some modification, the infrastructure of the existing power distribution systems can be used to provide data communication in addition to power delivery, thereby forming a power line communication system (PLCS). In other words, existing power lines, that already have been run to many homes and offices, can be used to carry data signals to and from the homes and offices. These data signals are communicated on and off the power lines at various points in the power line communication system, such as, for example, near homes, offices, Internet service providers, and the like.
Power distribution systems include numerous sections, which transmit power at different voltages. The transition from one section to another typically is accomplished with a transformer. The sections of the power distribution system that are connected to the customers premises typically are low voltage (LV) sections having a voltage between 100 volts (V) and 240V, depending on the system. In the United States, the LV section typically is about 120V. The sections of the power distribution system that provide the power to the LV sections are referred to as the medium voltage (MV) sections. The voltage of the MV section is in the range of 1,000V to 100,000V. The transition from the MV section to the LV section of the power distribution system typically is accomplished with a distribution transformer, which converts the higher voltage of the MV section to the lower voltage of the LV section.
In a power line distribution system, up to ten (and sometimes more) customer premises typically will receive power from one distribution transformer via their respective LV power lines. These LV power lines constitute infrastructure that is already in place. Thus, it would be advantageous for a communications system to make use of this existing infrastructure in order to save time and reduce costs of the installation. Thus, many PLCS communicate data via the MV power line and sometimes also via the LV power lines.
As is known to those skilled in the art, numerous MV power lines often extend from a single substation where they are supplied power. Typically, each MV power line is comprised of three phase conductors (e.g., phase A, phase B, and phase C), with each phase conductor carrying a power signal that is phase shifted approximately one hundred twenty degrees from the power signal on the other phase conductors. Typically, the phase conductor of a medium voltage power line will be electrically connected to the corresponding phase of one or more other MV power lines at the substation. For example, the phase A of a numerous MV power lines extending from the substation may be electrically connected to a first bus bar, the phase B conductors are connected to a second bus bar, and the phase C conductors electrically connected to a third bus bar. Consequently, any PLC data signals coupled to any phase conductor at the substation will be transmitted down all of the MV power lines (or at the very least, transmitted down one phase of each three phase power line extending from the substation).
Consequently, it would be desirable to isolate each MV power line so that simultaneous communications can take place separately on each MV power line. The present invention provides one system and method of isolating the MV power lines.
These and other advantages are provided by various embodiments of the present invention.